A media gateway is a device that sends and receives voice packets over a packet network and that may also interface with a circuit-switched network. On the packet side, a media gateway may send and receive voice packets over an IP network. Each connection or path between media gateways over which IP-encapsulated voice packets travel is referred to as a link, which is analogous to a channel in a circuit-switched network.
In order to provide high reliability, link redundancy is important with media gateways. One popular link redundancy design is 1:1 link redundancy where an active link, also referred to as a protected link, carries voice traffic, while a standby mate link, referred to as a protecting link, operates in a hot standby mode to take over if the active link fails. In order to achieve such redundancy, the pair of active and standby links needs to appear to the IP network as if they are in a single LAN segment. Thus, active and standby links are required to be bridged into a single LAN segment in order to achieve hot standby protection.
One existing approach to providing link redundancy is to use external Ethernet switches to switch traffic from an active link to a standby link when the active link fails. FIG. 1 illustrates an external Ethernet switch approach. In FIG. 1, media gateway 100 is connected to IP network 102 via a pair of external Ethernet switches 104 and IP edge routers 106. Media gateway 100 includes a first line card 108 functioning as an active card and a second line card 110 functioning as a standby card. Active card 108 is connected to active link 112, and standby card is connected to standby link 114.
In operation, when active link 112 fails, a card switchover occurs within media gateway 100, and Ethernet switch 104 is configured to forward traffic to standby link 114. Similarly, media gateway 100 sends outbound traffic over standby link 114.
One problem with using additional Ethernet switches to provide link redundancy is that this approach introduces additional switches in the path between media gateway 100 and edge routers 106. Adding additional Ethernet switches increases equipment costs and increases the number of potential points of failure in the network. Another problem with this approach is that a card switchover is required. As used herein, the term “card switchover” refers to one card taking over the operations of another card. In a media gateway context, a card switchover may include transitioning all of the connection information regarding which voice servers are associated with which connections from the active card to the standby card.
Another general approach to providing link redundancy is Cisco's Bridged Virtual Interface (BVI) or Switched Virtual Interface (SVI). FIG. 2 illustrates the BVI concept. In FIG. 2, traffic from a routed interface E3 can be switched to any or all of three bridged links E0-E2. One problem with this solution is that it requires that routers perform both Ethernet bridging and switching functions.
Additional problems with the BVI/SVI approach include the fact that bridged links must reside in the same hardware device, bridged links are always treated equally, and there are no hot standby NIC cards. Further problems with the BVI/SVI approach are that configuration is on a per VLAN basis, and thus support of multiple VLANs requires multiple bridges to be configured individually. Further, the BVI/SVI concept is typically applied to IP routers or Ethernet bridges, rather than end devices, such as media gateways. In addition, using a single hardware device to implement a BVI or SVI introduces a single point of failure.
Accordingly, there exists a need for methods, systems, and computer program products for implementing link redundancy in a media gateway.